Hepatocellular carcinoma (HCC) is a leading cause of death worldwide, and is rapidly increasing in prevalence in the United States. Current systemic therapies for the large proportion of HCC patients with advanced, nonresectable disease have been largely unsuccessful;thus, a clear need exists to develop effective, life- prolonging therapeutic strategies for this disease. The PI's laboratory has devoted vital resources to developing novel oral, small-molecule agents that target the molecular and cellular defects in HCC cells that make the clinical management of this disease so challenging. In this project, we focus on the mechanistic investigation and structural optimization of a novel class of protein kinase C (PKC)d-targeted agents by using FTY720, an immunosuppressive agent, as a scaffold. This study stems from our mechanistic finding that FTY720 triggers apoptosis in HCC cells by facilitating the activation of ROS-PKCd signaling. The following aims constitute the foci of this investigation: (1) to conduct structural optimization of FTY720 and mechanistic validation of optimal derivatives;and (2) to assess the in vivo effect of structurally optimized (S)-FTY2 derivatives on suppressing HCC xenograft growth. In Aim 1, lead optimization of FTY720 is directed at separating the immunosuppressive activity of FTY720 from its effects on ROS-PKCd signaling. (S)-FTY2, which represents a lead compound in this regard, will then be structurally optimized using a bioassay-guided, two-tiered strategy involving cell survival assays and Western blotting to screen against a (S)-FTY2-based compound library to generate potent PKCd-targeted agents. In Aim 2, the in vivo efficacies of optimal derivatives in suppressing the growth of HCC tumors will be examined in both orthotopic and ectopic xenograft tumor models. We expect the proposed studies to yield data in support of our hypothesis that targeting ROS- PKCd signaling by small-molecule agents represents a therapeutically relevant approach to treat HCC, and ultimately lead to new approaches that will improve the treatment of HCC and increase the survival of HCC patients. PUBLIC HEALTH RELEVANCE:Hepatocellular carcinoma (HCC) is a leading cause of death worldwide, and is rapidly increasing in prevalence in the United States. Our overall research goal is to develop novel therapeutic agents that target the molecular and cellular defects in HCC cells that make the clinical management of this disease so challenging. We expect that this project will ultimately yield new drugs that will improve the treatment of HCC and increase the survival of HCC patients.